全文获取类型
收费全文 | 115957篇 |
免费 | 11675篇 |
国内免费 | 6825篇 |
专业分类
电工技术 | 8489篇 |
综合类 | 9902篇 |
化学工业 | 15215篇 |
金属工艺 | 6506篇 |
机械仪表 | 6535篇 |
建筑科学 | 6954篇 |
矿业工程 | 4010篇 |
能源动力 | 3124篇 |
轻工业 | 13255篇 |
水利工程 | 3276篇 |
石油天然气 | 3229篇 |
武器工业 | 1593篇 |
无线电 | 10642篇 |
一般工业技术 | 10070篇 |
冶金工业 | 15247篇 |
原子能技术 | 1616篇 |
自动化技术 | 14794篇 |
出版年
2024年 | 644篇 |
2023年 | 1698篇 |
2022年 | 4027篇 |
2021年 | 5143篇 |
2020年 | 3609篇 |
2019年 | 2628篇 |
2018年 | 2885篇 |
2017年 | 3185篇 |
2016年 | 2997篇 |
2015年 | 4419篇 |
2014年 | 5506篇 |
2013年 | 6988篇 |
2012年 | 8175篇 |
2011年 | 8625篇 |
2010年 | 8075篇 |
2009年 | 7532篇 |
2008年 | 7614篇 |
2007年 | 7457篇 |
2006年 | 6373篇 |
2005年 | 4991篇 |
2004年 | 3954篇 |
2003年 | 3149篇 |
2002年 | 3174篇 |
2001年 | 2816篇 |
2000年 | 2073篇 |
1999年 | 1313篇 |
1998年 | 4208篇 |
1997年 | 2535篇 |
1996年 | 1741篇 |
1995年 | 1073篇 |
1994年 | 856篇 |
1993年 | 944篇 |
1992年 | 328篇 |
1991年 | 290篇 |
1990年 | 285篇 |
1989年 | 260篇 |
1988年 | 233篇 |
1987年 | 205篇 |
1986年 | 197篇 |
1985年 | 217篇 |
1984年 | 99篇 |
1983年 | 118篇 |
1982年 | 128篇 |
1981年 | 151篇 |
1980年 | 185篇 |
1979年 | 97篇 |
1978年 | 73篇 |
1977年 | 271篇 |
1976年 | 494篇 |
1975年 | 66篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
在公交时间表下给定起始和目标站点,路径规划查询返回一组到达时间早和换乘次数少的帕雷托最优路径.现有的索引方法需要大量运行时内存.本文提出主存空间高效的索引方法(a-)PAINT.(a-)PAINT对每个站点v预计算一组标签,使得对于从站点s到站点d的查询可以通过匹配s和d相关的标签高效地生成查询结果的一条路径.PAINT对任意查询返回最优路径.a-PAINT只需要很小的预处理开销,但可能返回多一趟换乘的次优路径.用真实的公交时间表与模拟查询测试,PAINT具有合理的预处理开销.a-PAINT需要更少量的预处理开销,在大规模公交网络下准确率达90%. 相似文献
13.
介绍了国内外物联网技术产业发展现状.分析我国物联网技术存在的短板,并从技术研发、产业联盟组建和商业模式推广等方面提出了促进我国物联网产业发展的若干建议. 相似文献
14.
16.
Laís D. Silva Fernanda C. Puosso Viviane O. Soares Oscar Peitl Filho Simone do R.F. Sabino Francisco C. Serbena Murilo C. Crovace Edgar D. Zanotto 《Ceramics International》2021,47(13):18720-18731
Bioactive glasses and glass-ceramics (GCs) effectively regenerate bone tissue, however most GCs show improved mechanical properties. In this work, we developed and tested a rarely studied bioactive glass composition (24.4K2O-26.9CaO-46.1SiO2-2.6P2O5 mol%, identified as 45S5-K) with different particle sizes and heating rates to obtain a sintered GC that combines good fracture strength, low elastic modulus, and bioactivity. We analyzed the influence of the sintering processing conditions in the elastic modulus, Vickers microhardness, density, and crystal phase formation in the GC. The best GC shows improved properties compared with its parent glass. This glass achieves a good densification degree with a two-step viscous flow sintering approach and the resulting GC shows as high bioactivity as that of the standard 45S5 Bioglass®. Furthermore, the GC elastic modulus (56 GPa) is relatively low, minimizing stress shielding. Therefore, we unveiled the glass sintering behavior with concurrent crystallization of this complex bioactive glass composition and developed a potential GC for bone regeneration. 相似文献
17.
Davide De Biase Giuseppe Piegari Francesco Prisco Ilaria Cimmino Ilaria dAquino Valeria Baldassarre Francesco Oriente Serenella Papparella Orlando Paciello 《International journal of molecular sciences》2021,22(7)
Sarcopenia is defined as the age-related loss of skeletal muscle mass, quality, and strength. The pathophysiological mechanisms underlying sarcopenia are still not completely understood. The aim of this work was to evaluate, for the first time, the expression of NLRP3 inflammasome in bovine skeletal muscle in order to investigate the hypothesis that inflammasome activation may trigger and sustain a pro-inflammatory environment leading to sarcopenia. Samples of skeletal muscle were collected from 60 cattle belonging to three age-based groups. Morphologic, immunohistochemical and molecular analysis were performed to assess the presence of age-related pathologic changes and chronic inflammation, the expression of NLRP3 inflammasome and to determine the levels of interleukin-1β, interleukin-18 and tumor necrosis factor alpha in muscle tissue. Our results revealed the presence of morphologic sarcopenia hallmark, chronic lymphocytic inflammation and a type II fibers-selective NLRP3 expression associated to a significant decreased number of immunolabeled-fibers in aged animals. Moreover, we found a statistically significant age-related increase of pro-inflammatory cytokines such as interleukin-1β and interleukin-18 suggesting the activation of NLRP3 inflammasome. Taken together, our data suggest that NLRP3 inflammasome components may be normally expressed in skeletal muscle, but its priming and activation during aging may contribute to enhance a pro-inflammatory environment altering normal muscular anabolism and metabolism. 相似文献
18.
Stefano Mariani Antonino Amedeo La Mattina Alessandro Paghi Lucanos Strambini Giuseppe Barillaro 《Advanced functional materials》2021,31(26):2100774
Here, a fluoride-assisted route for the controlled in-situ synthesis of metal nanoparticles (NPs) (i.e., AgNPs, AuNPs) on polydimethylsiloxane (PDMS) is reported. The size and coverage of the NPs on the PDMS surface are modulated with time and over space during the synthetic process, leveraging the improved yield (10×) and faster kinetics (100×) of NP formation in the presence of F− ions, compared to fluoride-free approaches. This enables the maskless preparation of both linear and step gradients and patterns of NPs in 1D and 2D on the PDMS surface. As an application in flexible plasmonics/photonics, continuous and step-wise spatial modulations of the plasmonic features of PDMS slabs with 1D and 2D AgNP gradients on the surface are demonstrated. An excellent spatially resolved tuning of key optical parameters, namely, optical density from zero to 5 and extinction ratio up to 100 dB, is achieved with AgNP gradients prepared in AgF solution for 12 minutes; the performance are comparable to those of commercial dielectric/interference filters. When used as a rejection filter in optical fluorescence microscopy, the AgNP-PDMS slabs are able to reject the excitation laser at 405 nm and retain the green fluorescence of microbeads (100 µm) used as test cases. 相似文献
19.
Romero-Garcés A. Salles De Freitas R. Marfil R. Vicente-Chicote C. Martínez J. Inglés-Romero J. F. Bandera A. 《Multimedia Tools and Applications》2022,81(3):3603-3628
Multimedia Tools and Applications - The design of robots capable of operating autonomously in changing and unstructured environments, requires using complex software architectures in which,... 相似文献
20.